1. Field of the Invention
The present invention relates to printing apparatus and particularly to a thermal transfer printing apparatus which can perform multicolor printing and the like.
2. Description of the Background Art
A conventional multicolor thermal transfer printing apparatus includes: a carriage which is provided with a printing head and reciprocates in scanning directions; a cassette stand which is placed over the carriage and where a plurality of ink ribbon cassettes are stacked; and a lifting device which moves the cassette stand upward or downward with respect to the carriage to select a desired ink ribbon among the plurality of ink ribbon cassettes to be opposite to a printing head during plural times of scanning operations of the printing head.
By moving the cassette stand upward and downward, it is possible to locate the desired ink ribbon opposite to the printing head so that printing can be made on printing paper. In this case, if ink ribbons of three colors of yellow, magenta, and cyan are used for the plurality of ink ribbon cassettes subtractive color mixing of those three primary colors is made in the same areas of the printing paper and thus eight colors of blue, cyan, green, yellow, red, magenta, and white (the paper's color) are obtained. Thus, a multicolor image is printed.
In the above-mentioned background art, if the ribbon in an arbitrary stage comes to an end, no means is provided to detect it. Consequently, the printing head is continuously conducted and printing continues, which sometimes makes it impossible to print an image in a desired color.
In addition, if the user becomes aware of the end of the ribbon and stops the printing, it is necessary to return the carriage to a prescribed position for replacement of the ink ribbon with another ribbon. In consequence, troublesome operation is required if printing is to be restarted since it is necessary to manually move the carriage to the previous stop position of the ribbon after replacement of the ribbon with the new one. In addition, since this operation is manually carried out, it is difficult to effect an accurate positioning at the time of restarting the printing.
In the above-mentioned background art, it sometimes happens that the user forgot attaching a black ribbon and erroneous printing with the black ribbon occurs in color printing. In such a case, the user is not aware of the attachment of the black ribbon until start of printing. In consequence, it is necessary to change the black ribbon for a color ribbon and to start printing on new printing paper and thus the work in such a case is troublesome.